The metabosism of protaglandins either results in their biological inactivation or in a conversion to another class of prostaglandins with somewhat different physiological properties. The objective of the proposed research is to study the enzymes catalyzing prostaglandin, prostacyclin, and thromboxane metabolism in the human placenta. The enzymes will be isolated and purified, their characteristics will be established, and the mechanisms controlling their activity will be sought.